Optical scanners direct a light beam to scan the surface of a remote object. This is typically accomplished by using a mirror which reflects the beam toward a desired location on the object surface. Usually, the mirror is mounted onto a rotatable shaft assembly which is driven by a motor. Thus, as the motor drives the shaft to rotate the mirror, the beam is swept across the surface of the remote object.
The precision of an optical scanner depends largely on its ability to steer the beam without being disturbed by various stimuli which divert the beam from its intended path. One type of such stimulus is nontorsional vibration of the shaft that rotates the mirror.
Such vibration may be externally induced by disturbances that jar the base of the scanner, causing the shaft to vibrate in the nontorsional direction. Similarly, imbalances within the rotational system of the scanner may cause nontorsional vibration of the shaft. These imbalances manifest themselves, in particular, when a saw-tooth signal drives the scanner. Such waveform causes the scanner to sweep the beam across the object surface and abruptly snap back at the end of each sweep. This torsionally shocks the shaft assembly and causes it to vibrate in the lateral or off-axis direction.
It is desirable, therefore, to reduce nontorsional vibration of the shaft during scanner operation.